SCIENTIFIC SUMMARY. 
95 
He states that as all the other solipecles are either Asiatic or African, it is 
extremely unlikely that the horse originated in Europe. 
Relation of Astronomy to Geology. — The study of geological phenomena 
in their relation to astronomical variations in the position of the earth has 
been very successful in the hands of Mr. James Croll, whose last paper on 
the change in the obliquity of the ecliptic, and its influence on the climate 
of the polar regions and level of the sea,” we have had tlie pleasure to 
receive, hlr. Croll’s views are somewhat opposed to the current method of 
explaining geological phenomena, such as those of the glacial periods, but 
they are supported by a stern logic, and by a thorough acquaintance with 
both geology and astronomy, which cannot fail to give his opinions a 
powerful influence. So far as we can observe, his theory does not differ in 
many serious particulars from that propounded by Mr. Adhemar some years 
ago. 
Volcanic Rruption in the Azores. — M. Fouque, who was sent by the French 
Government to investigate this matter, has sent in his report. After con- 
siderable trouble he succeeded in collecting the gas, which is still bubbling 
up through the sea, in sufficient quantities for analysis. He states that it 
is quite free from carbonic acid and contains a very large proportion of 
oxygen. — Vide Comptes Rendus, Oct. 21. 
The Geology of Wells. — We are glad to see that in the last report of the 
medical officer of the Privy Council the important question of the geolo- 
gical character of wells has not been overlooked. The relation of geolog}’ 
to hygiene is one of considerable moment, and it is satisfactory to find that 
the State Sanitary Department has taken the initiative in pointing out this 
relationship to those engaged in inquiries upon questions of public health. 
Out of a list of 90 wells, of ascertained depth, 5 were between 40 and 60 
feet ] 21 were between 30 and 40 feet ; 24 were between 20 and 30 feet, 
whilst 40 were only from 9 to 20 feet in depth. When, notwithstanding 
all the efforts to the contrary, the sewage of a population like London is 
daily affecting the subsoil to a greater or less extent, it stands to reason 
that all superficial sources of water- supply within the town-area must be 
seriously vitiated by ancient cesspools and other unremoved nuisances 
Avhich yet haunt many of the poorer suburban quarters of our great citv. 
In addition to the Tabulated List of Wells in London, there are 15 
tables, comprising upwards of 206 ascertained borings along the various 
lines of the Metropolitan Main Drainage Works. 
The Granites of Leinster and Donegal. — In the course of the controversv, 
not yet concluded, concerning the origin of granite, Mr. W. H. S. Westropp 
has drawn the attention of geologists to a question of some seriousness. He 
asks. Are we to suppose that notwithstanding the vast difference between 
their modes of occurrence in the field, the granites of Leinster and the 
granitoid rocks of Donegal must have had a like origin, merely because thev 
have a somewhat similar mineral composition, both containing quartz, feld- 
spar, and mica ? But have these rocks an identical mineral composition ? So 
far as his experience goes, most assuredly not. They vary in appearance, tex- 
ture, mode of aggregation of the component minerals j the quartz has a dif- 
ferent look, difficult to describe, but, once seen and observed, not easily to be 
forgotten. But above all, they differ widely in their feldspathic constituents, 
